Yikes, as if we didn't already think the First World War claimed enough victims: A French historian says the number of soldiers killed in the Great War has been vastly understated — a death count too low by as many as one million.

Above: Serbian prisoners of war are arranged in a semi-circle and executed by an Austrian firing squad, 1917. Credit Underwood & Underwood/Wikimedia Commons.

Traditionally, historians have settled on the figure of nine million soldiers killed during WWI. This death count is now being challenged by Antoine Prost, Professor Emeritus at Pantheon-Sorbonne University in Paris. In an article published in the final volume of the Complete Cambridge History of the First World War, Prost claims the death toll should be closer to ten million.

"Official statistics fail to take into account the soldiers who died as a result of illness or while being detained in prisoner-of-war camps," Prost told FRANCE 24. "The armies often rushed to give their figures, seeking to play down their losses."

Here's some of what he found:

France: The military had only counted those who died while serving in the army (around 1,325,000), excluding the 70,000 who died of war-related illnesses upon returning home.

Germany: Its military leaders simply stopped counting casualties by late July 1918 — some four months before the armistice.

Russia: Soviet stats omitted the POWs who died in German camps, around 200,000 people.

USA: Bucking the trend, the U.S. magnified its losses to establish itself as a major military power; U.S. losses are estimated between 110,000 and 120,000 — but 35,000 of American soldiers actually died of the Spanish Flu before making it home.

Another issue is how different armies buried their dead. The British, for example, built military cemeteries along the frontline. This contributed to significant confusion.

France was less organized:

By the time the government set up a national commission to deal with the issue, in November 1918, many families had already travelled to the front to look for their lost ones.

"This was illegal, but if the families had enough money they could bribe undertakers to take the bodies back home," says Prost.

The government eventually bowed to pressure from the public. More than 240,000 bodies were identified and sent back home, while the rest were buried in military cemeteries.